The potential usefulness of specific transfer factor in immuno- intervention of certain human diseases is widely recognized. Current sources of specific transfer factor are totally inadequate. It is proposed that attempts be made to develop lymphoid cell lines from cells with specific cellular immunity and to determine if such cell lines maintain their specific immunocompetence. If so, such cell lines should be an ideal source of specific transfer factors for clinical use. Human peripheral lymphocytes with cellular immunity against a specific antigen will be selected by existing procedures. The selected lymphocytes will then be induced to multiply rapidly and persistently by infection with the EB virus. Standard procedures for the extraction of transfer factor from human peripheral lymphocytes will be applied to these lymphoid cell lines, and the product will be tested for specific transfer factor activity by determining its capability to confer on non-sensitized lymphocytes the ability to undergo blastoid transformation and to release macrophage migratory inhibitory factor in the presence of specific antigen.